Various performance tests such as tests for fuel economy and exhaust emission are conventionally performed by operating a test vehicle on a chassis dynamometer. In such a performance test, the vehicle is driven by performing the accelerator operation, brake operation and shift operation (and clutch operation in the case of a vehicle with a manual transmission) properly according to a drive pattern defined by time and vehicle speed like a fuel consumption test (JC08 mode) shown in FIG. 9, for example.
In a running operation, as shown in FIG. 10, as an example, the vehicle is required to run in an inside zone between an upper limit allowance line and a lower limit allowance line determined by a standard point of a standard mode (standard running mode) determined by time instant and vehicle speed and a rectangle determined by allowable values or allowable errors of ±2.0 km/h (±2.0 km/h in Japan and Europa, ±2.0 mile/h in U.S.A.) and ±1.0 sec.
In FIG. 10, the upper limit allowance line is a line obtained by connecting upper limit points of different time instants. Each of the upper limit points is a point spaced from the standard point of the standard mode at a given time instant, by +2.0 km/h and −1.0 sec. The lower limit allowance line is a line obtained by connecting lower limit points of different time instants. Each of the lower limit points is a point spaced from the standard point at a given time instant in the standard mode, by 2.0 km/h and +1.0 sec.
In this case, the vehicle speed of the test vehicle is controlled in a vehicle speed following control or follow-up control by the accelerator operation and the brake operation of the test vehicle, and the chassis dynamometer is controlled in a drive control according to a load drive pattern depending on the vehicle speed so as to produce an imaginary road surface resistance (load) with the roller(s) contacting with the tire(s) of the test vehicle.
The accelerator and brake operations may be performed by a human driver or may be performed by a drive operation robot.
For the above-mentioned control of the vehicle speed, for example, vehicle speed data is obtained by drive control along the standard mode according to a predetermined drive pattern, and the thus-obtained vehicle speed data is accumulated. At the time of testing, the thus-accumulated vehicle speed data is used as a vehicle speed command, and the vehicle speed following control is performed in accordance with a vehicle speed deviation between the vehicle speed command and a sensed actual vehicle speed.
Patent Document 1 discloses a brake operation timing automatic judging circuit for changeover between accelerator and brake in accordance with the above-mentioned vehicle speed deviation.